مهندسی مکانیک مدرس

مهندسی مکانیک مدرس

بررسی تاثیر یک روش تغییر شکل پلاستیکی شدید ترکیبی بر رفتار تغییر شکل گرم آلیاژ منیزیم Mg-3Al-1Zn

نویسندگان
1 دانشگاه تهران
2 پارک علم و فناوری استان هرمزگان-رئیس پارک و عضو هیات علمی دانشگاه هرمزگان
3 استادیار، مهندسی مکانیک، دانشگاه هرمزگان
4 استادیار دانشگاه تهران
5 استاد/دانشگاه تهران
چکیده
هدف اصلی این پژوهش، تهیه‌ی لوله‌های جدار نازک فوق ریزدانه از جنس آلیاژ منیزیم AZ31 با داکتیلیتی بالا در دمای بالا است. بدین منظور، یک روش تغییر شکل پلاستیک شدید ترکیبی که شامل روش فشار در کانال لوله‌ای موازی زاویه‌دار یا پی‌تی‌کپ و روش اکستروژن معکوس لوله یا تی‌بی‌ای است، به کار گرفته شد. به طوری که ابتدا روش پی‌تی‌کپ بر روی نمونه‌های لوله‌ای شکل، در دمای 300°C انجام شد و سپس نمونه‌ها در دمای 300°C مورد فرآیند تی‌بی‌ای واقع شدند. بعد از انجام پی‌تی‌کپ، یک ساختار گردنبندی که شامل دانه‌های بزرگ احاطه شده با دانه‌های ریز تبلور مجدد شده بود، مشاهده گردید و میانگین اندازه دانه از 520 µm به 11.1 µm رسید. در مرحله بعد، پس از انجام تی‌بی‌ای، مشاهده شد که ساختاری فوق ریزدانه با اندازه دانه‌ی میانیگن 8.6 µm پدید آمد. پس از انجام این فرآیند ترکیبی، مقدار سختی نمونه‌ها از37 HV به69 HV افزایش یافت. مطالعات تست کشش گرم در دمای 400°C نشان‌گر وقوع تغییر طول تا شکست 181% درصد برای نمونه‌ی پی‌تی‌کپ و تی‌بی‌ای شده بود در حالی‌که همین مقدار برای نمونه‌ی خام اولیه برابر 55% درصد بود. تصاویر شکست‌نگاری اس‌ای‌ام گویای آن بودند که در نمونه‌های آزمون کشش گرم، غالبا شکست داکتیل اتفاق افتاده است که ناشی از جوانه زدن میکروفضاهای خالی و متعاقبا رشد و تداخل آن‌ها با یک‌دیگر بوده است.
کلیدواژه‌ها

موضوعات


عنوان مقاله English

Evaluation of the effects of a combined severe plastic deformation method on the hot deformation behavior of Mg-3Al-1Zn magnesium alloy

نویسندگان English

M. Eftekhari 1
Ali Fata 2
Ali Fata 3
M. Mosavi 5
1 Tehran Uni
2 Hormozgan
3 Hormozgan
5 Uni Tehran
چکیده English

The main goal of this study is achieving thin-walled AZ31 magnesium alloy tubes with high ductility at elevated temperature. For this purpose, a combined severe plastic deformation method, including parallel tubular channel angular pressing (PTCAP) and tube backward extrusion (TBE) was used. First, PTCAP process was applied on tubular samples at 300°C and then, TBE process was performed at 300°C. After PTCAP, a necklace like microstructure, large gains surrounded by a large number of tiny recrystallized ones, was observed and the average grain size of the material decreased from 520 µm to 11.1 µm. At the next stage, After TBE, an ultra-fine grain microstructure with an average grain size of 8.6 µm was formed. After performing this combined method, the hardness value of the PTCAP and TBE processed sample increased from 37 HV to 69 HV. Hot tensile testing studies at 300°C revealed an elongation to failure value of 181% for the PTCAP and TBE processed sample, while this value for as-received sample was 55%. Fractographic SEM images showed that predominately ductile fracture was occurred in all hot tensile specimens due to nucleation of microvoids and their subsequent growth and coalescence with each other.

کلیدواژه‌ها English

Severe plastic deformation
AZ31 Alloy
PTCAP
TBE
Ultra-fine grain
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